Two-dimensional (2D) semiconductors, such as transition metal dichalcogenides, provide an opportunity for beyond-silicon exploration. However, the lab to fab transition of 2D semiconductors is still in its preliminary stages, and it has been challenging to meet manufacturing standards of stability and repeatability. Thus, there is a natural eagerness to grow wafer-level, high-quality films with industrially acceptable scale–cost–performance metrics. Here we report an improved chemical vapour deposition synthesis method in which the controlled release of precursors and substrates predeposited with amorphous Al₂O₃ ensure the uniform synthesis of monolayer MoS₂ as large as 12 inches while also enabling fast and non-toxic growth to reduce manufacturing costs. Transistor arrays were fabricated to further confirm the high quality of the film and its integrated circuit application potential. This work achieves the co-optimization of scale–cost–performance metrics and lays the foundation for advancing the integration of 2D semiconductors in industry-standard pilot lines.